1. Field of the Invention
The invention relates to gamma correction for a video signal.
2. Discussion of Prior Art
The luminance of an image point on a cathode ray tube (CRT) is not proportional to the voltage applied to the tube at the same moment. On the contrary, luminance is a power function of said voltage. It is conventional to call the value of the exponent of said power function "gamma".
Various factors cause the value of gamma to lie in the range a little more than 0 to about 5. However, this is a design choice, and the value remains constant for a given device.
There are various proposals in existence for providing gamma correction. However, the circuits that have been proposed do not provide full satisfaction, either because they are excessively complex and expensive, or else because they turn out to be unsuitable for operation with the television of the future, i.e. with definition that is higher than present practice.